Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at February 23, 2016

Gastroenteritis, commonly called stomach flu or stomach bug, is a common illness that occurs when the stomach and intestines become irritated. Although it is often referred to as a type of flu, it has no relation to the standard type of flu (influenza).


Definition & Facts

The medical term gastroenteritis is a compound word formed from a term for the stomach and digestive system plus the suffix "itis" to indicate an inflammation or irritation. Most childhood cases of gastroenteritis are caused by a virus from the family of the rotavirus while adults commonly get gastroenteritis from a rotavirus, norovirus, fungi, parasites or a bacterial infection.

The most common way to contract gastroenteritis is by physical contact with an infected person or consuming food or water that has been contaminated with a fungus, virus, or parasite. The latter is also known as food poisoning or foodborne illness.

In developed countries, gastroenteritis can usually be treated without the need of medical intervention but the illness can often result in death in individuals with a compromised immune system or for otherwise healthy people in areas of the world where people lack access to clean water.

Symptoms & Complaints

Most people can immediately identify a case of gastroenteritis after they experience a case of very watery (and non-bloody) diarrhea accompanied by vomiting, nausea, and/or stomach cramps. Multiple bouts of watery diarrhea can quickly deplete the body of vital fluids so gastroenteritis is often accompanied by signs of dehydration like dry skin, dry mouth, feeling extremely thirsty, and feeling dizzy, confused, and lightheadedness.

Depending on how the condition was contracted, symptoms of gastroenteritis will appear between one and three days after the person became infected. Most cases of gastroenteritis last just one to two days but especially persistent cases can last as long as 10 days.

Anyone who is unable to keep water down for longer than 24 hours, begins vomiting blood, is excessively dehydrated or has a high grade fever (104 degrees Fahrenheit or 40 degrees Celsius or higher) should seek medical attention right away.


The most common cause of gastroenteritis in children is an infection caused by the rotavirus. The viral gastroenteritis infection starts when children put objects in their mouth that are contaminated but can also occur when coming in contact with infected adults. Some adults who have a rotovirus may not show any symptoms and thus unwittingly pass on the rotovirus to children in their care. Babies often get gastroenteritis after being fed with improperly sanitized bottles.

Both adults and children can acquire gastroenteritis by coming in contact with a norovirus, usually transmitted via food or drink. While personal contact with an infected person can spread the norovirus responsible for gastroenteritis, most cases of the illness come from direct consumption of infected water or food.

In the developed world, the most common transmission route for the viruses and bacteria that causes gastroenteritis is when one person handles food or drink without having washed their hands after using the bathroom, known as the fecal-oral route.

Several different species of microbes, including giardia, can cause gastroenteritis. These microscopic protozoa enter the body when people consume water that has not been sufficiently purified. Bacterial gastroenteritis can be caused by infection with salmonella, shigella, and E. coli.

Diagnosis & Tests

There is no known test for diagnosing gastroenteritis. Doctors usually identify the illness based on a clinical assessment of the person's symptoms and complaints. An official test for gastroenteritis is not necessary because the condition usually resolves on its own.

Doctors may perform a number of secondary tests on individuals with gastroenteritis such as measuring how well the kidney is functioning as well as the electrolyte balance to ensure that proper measures are being taken to combat dehydration.

Doctors may also perform tests to make sure that someone with the symptoms of gastroenteritis is not actually suffering from similar illnesses, including irritable bowel disease, short bowel syndrome, appendicitis, celiac disease, a urinary tract infection or diabetes.

Treatment & Therapy

The most critical step in treating gastroenteritis is to consume plenty of clean water to replace the fluids being lost due to diarrhea and/or vomiting. Antiemetic drugs may be used to reduce vomiting. Gastroenteritis can cause severe cases of dehydration that can lead to severe permanent damage or even death.

Bed rest and the consumption of plenty of replacement fluids is the best course of therapy for most with gastroenteritis. If symptoms persist or become worse, it is advised to seek medical attention to rule out other more severe illnesses. In rare cases, antibiotics may be prescribed to combat bacterial gastroenteritis.

Prevention & Prophylaxis

A number of precautions can be taken to prevent gastroenteritis. The most important step in protecting against contracting the illness is regular hand washing with soap after trips to the bathroom and to make sure that anyone who handles food or water does the same.

Drinking clean, safe water is also a key step to preventing contracting a case of gastroenteritis. Water from streams, lakes, and rivers should always be boiled to eliminate the chance of bacterial infection. When traveling to less developed nations, only bottled water should be consumed.

Young children can get a vaccine against the rotovirus, the principle cause of gastroenteritis in children. Baby bottles should always be properly sterilized before use and mothers are recommended to breastfeed whenever feasible.

People with a compromised or weakened immune system are especially vulnerable to viral infections including gastroenteritis. Anyone living in an institutional setting or spending a lot of time with large groups should make sure that that all caregivers follow proper sanitary procedures to avoid passing along the virus.

Medical statisticians have confirmed that viral infections in general, including those that cause gastroenteritis, are more frequent and severe during winter months. There is some evidence to suggest that eating undercooked or raw oysters and other forms of shellfish may increase the risk of transmitting foodborne pathogens that cause gastroenteritis.